Fungi directly affect the health of animals and humans as pathogens, particularly in immunologically compromised individuals. They also are responsible for causing disease and spoilage of food crops that indirectly impact human health. An understanding of the molecular mechanisms governing gene expression in the filamentous fungi will help provide the insight needed to develop strategies against fungal infection of living organisms. Asexual development is a critical phase in the fife cycle of most fungi. This project will focus on understanding the interaction of development and gene expression. The filamentous ascomycete Neurospora crassa is particularly suited for these studies because of the wealth of genetic and biochemical data available and its simple development during asexual spore formation. Recent progress in applying molecular biological approaches to the study of N. crassa has greatly facilitated examination of asexual development. N. crassa is one of the most highly developed systems for analyzing gene expression in filamentous fungi. The specific goal of this project is to determine the genetic regulatory mechanisms involved in controlling asexual development in N. crassa. Promoter analyses will identify DNA sequence elements required for developmental expression of genes. Biochemical analyses of protein factors that bind to these DNA sequences will precisely define the interaction of cis- and trans-acting regulatory elements. In a complementary approach, mutants that are altered in the temporal or spatial regulation of developmentally expressed genes will be isolated. Characterization of these mutants will define the regulatory network involved in controlling spore formation in this fungus. This work will also contribute to our general understanding of gene expression in eukaryotic organisms.